Biology and management of dragon scale fern (Pyrrosia piloselloides L.)

Abstract

Pyrrosia piloselloides (Dragon scale) is an epiphytic fern that belongs to the family polypodiaceae. A study was conducted during the period of October 2021 to November, 2023 to understand the distribution, morphological characters, propagation methods, host range and allelopathic properties of Pyrrosia piloselloides and also to develop control/management measures against this fern. Pyrrosia piloselloides was mostly found on trees growing in humid and partial conditions. It is observed that the terminal branches of host plant dries initially followed by decline and die back of the plant under severe infestations. Survey was conducted in various areas of Kerala to assess the severity of infestation and crops infested. Severity of infestation was noticed in places near Periyar river basin in Ernakulam district followed by Alappuzha and Kottayam districts. Pyrrosia has a wide host range, mainly found on tree crops like teak, mahogany, wild jack, mastwood, banyan, golden shower, suicide tree, rain tree, peepal tree, nutmeg, mango, coconut, arecanut, neem, jack fruit, sapota, durian, clove, tamarind, garcinia, cocoa, tea, coast cottonwood and jungle geranium. Recently farmers from different locations of Kerala reported about the wide infestation of this fern and subsequent drying of the host plant due to the severe infestation. Severe infestation of this fern and economic loss were reported from nutmeg plantations in Ernakulam and hence a study was conducted. The Pyrrosia exhibits dimorphism in frond morphology; sterile and fertile fronds. Sterile fronds are light green and dark green in colour, responsible for photosynthesis. Leaves are seen as rounded, oblong, heart like, lanceolate and linear. On microscopic examination, it is observed that stomata are distributed only in lower surface of sterile fronds. Fertile fronds are mainly in linear shape, whitish green colour initially and turns brownish red on maturity. Spores are present on the lower surface of fertile fronds. Rhizome of P. piloselloides are slender, covered by scales, with enormous roots. Pyrrosia propagates mainly through spores. It can be propagated through rhizome cuttings also. The growth rate of rhizome varied in different hosts and seasons. On observation of rhizome growth on various tree crops like nutmeg, mango

and arecanut, growth was fastest in nutmeg tree. The fern grows at a rate of 1.54 cm per week in the wet season, whereas in dry season, 0.84 cm per week of growth. On analysis of various plant samples from different locations of Kerala, two species of Pyrrosia were identified; Pyrrosia piloselloides and Pyrrosia porosa. The common Pyrrosia species found in Kerala is P. piloselloides, which causes severe problems in crops. Application of aqueous extract of rhizome and whole plant extract of Pyrrosia at various concentrations of 1%, 2% and 4% did not show any allelopathic effect on the germination percentage, shoot length and fresh weight of test crop, cowpea. The phytochemicals screening of extracts were revealed the presence of phenols, flavonoids, tannins, terpenoids, carbohydrates and sterols. Evaluation of efficacy of physical removal from the host plant was conducted at farmers field. Physical removal was very effective in controlling Pyrrosia as no regrowth was observed up to one year. However, complete control is possible only if it is practiced in the initial stage itself. At advanced stage of infestation, physical removal cannot be recommended. Experiment of chemical method of control using different inorganic and organic herbicides were conducted in nutmeg plantations near Kalady, Ernakulam district. The herbicides tested were common salt (150g/l), copper sulphate (5g/l), 2, 4-D sodium salt (4g/l), imazethapyr (0.2 g/l), metsulfuron methyl (1g/10 l), ethrel (25 ml/l) and glufosinate ammonium (8 g/l). Among these chemicals, 2, 4-D, metsulfuron methyl and glufosinate ammonium showed total control of fern after 120 days of spraying. However, 2, 4-D sodium salt caused severe injury on the host plant after application. Other chemicals, metsulfuron methyl and glufosinate ammonium also caused injury to the host plant on application, but the leaves regenerated in 90-120 days of application. However if the infestation is very severe, application of metsulfuron methyl (1 g/10 l)and glufosinate ammonium (8 g/l)can be recommended. Pathological examination of Pyrrosia infested nutmeg branches indicated association of tree killing fungus, Lasiodiploida theobromae which causes decline and die back of trees was found.

Results of the study revealed that, physical removal of Pyrrosia from the host plant in initial stage itself could eradicate the problematic weed and reduce the economic loss. Prophylactic application of fungicides can be recommended for reducing the severity of infestation as the association of fungus, Lasiodiplodia theobromae was found in Pyrrosia infested branches.